Conventionally, when a crime or a legal conflict relating to computers such as unauthorized access or leakage of confidential information occurs, there have been proposed means or techniques that collect and analyze equipment, data, and electronic records required for investigation into the cause of the crime or legal conflict and clarify legal evidences of the crime or legal conflict.
Particularly, procedures such as eDiscovery (electronic discovery) are required for a civil lawsuit in the United State of America and both a plaintiff and a defendant involved in the lawsuit are liable to submit all pieces of related digital information as evidences. Therefore, they need to submit digital information recorded in computers and/or servers as the evidences.
Meanwhile, due to the rapid development and spreading of information technologies, most information in today's business world is produced by computers, so that digital information is abundant even within the same company.
Therefore, in the preparatory work of gathering evidentiary materials to be submitted to a court of law, mistakes can easily occur where even confidential digital information, which is not necessarily related with the relevant lawsuit, may be included in the evidentiary materials. Another problem is that confidential document information which is not related to the relevant lawsuit is submitted.
In recent years, techniques related to document information in forensic systems have been proposed in PTL 1 to PTL 3. PTL 1 discloses a forensic system that: designates a specific person from at least one or more users included in user information; extracts only digital document information which is accessed by the specific person on the basis of access history information about the designated specific person; sets accessory information indicating whether each document file of the extracted digital document information is related to a lawsuit or not; and outputs the document files related to the lawsuit on the basis of the accessory information.
Furthermore, PTL 2 discloses a forensic system that: displays recorded digital information; sets user-identifying information indicating to which one of users included in user information each of a plurality of document files is related; sets settings so that the set user-identifying information will be recorded in a storage unit; designates at least one or more users; searches for a document file in which the user-specifying information corresponding to the designated user is set; sets accessory information indicating whether the searched document file is related to a lawsuit or not, on a display unit; and outputs the document file related to the lawsuit on the basis of the accessory information.
Furthermore, PTL 3 discloses a forensic system that: receives designation of at least one or more document files included in digital document information; receives designation indicating into which language the designated document file should be translated; translates the designated document file into the designated language; extracts a common document file indicating the same content as the designated document file from the digital document information recorded in a recording unit; generates translation-related information indicating that the extracted common document file is translated by employing the translation content of the translated document file; and outputs a document file related to a lawsuit on the basis of the translation-related information.